1. Field of the Invention
This invention lies in the field of electroporation, the process by which exogenous molecular species are inserted into membranous structures by suspending the structures in a liquid solution of the exogenous species and applying an electric field to the resulting suspension. In particular, this invention addresses electroporation cuvettes.
2. Description of the Prior Art
Electroporation, or electric pulse-driven transfection, is widely used for impregnating membranous structures, such as living biological cells, liposomes, and vesicles, with exogenous molecules. The structures are typically suspended in an aqueous solution of the exogenous species in a high-conductivity buffer. Normal saline is commonly used as the buffer since, in addition to offering relatively low resistance to an electric current, normal saline provides an environment that is favorable to the viability of most membranous structures. The suspension is typically placed in a cuvette that is equipped with electrodes, and electroporation is performed in the cuvette.
A prime concern in any electroporation procedure is efficiency, which is defined as the number of membranous structures that are successfully impregnated in the procedure. The goal is to impregnate as many membranous structures in a given sample as possible and to cause each structure to receive as closely as possible the same number of molecules of the impregnant. Full uniformity is an elusive goal, however; a certain degree of variation is inherent in any electroporation procedure, due to the different locations and physical orientations of the membranous structures relative to the electric field. When the membranous structures are biological cells, a further source of variation is the range of maturity of the cells, since a typical cell population contains cells at various stages of their life cycles. A single cell line can therefore have cells of different diameters. The electric field intensity is determined by dividing the impressed voltage by the distance between the electrodes, but the voltage across a single cell will be proportional to the cell diameter. Thus, for a given field intensity, small cells will experience a relatively low voltage difference while the voltage difference experienced by large cells will be relatively high. If the voltage difference is too low, the cell walls will not become sufficiently porous to allow the molecules to penetrate, and if the voltage difference is too high, the resulting dipole moment will cause cell lysis.